A non-functioning tachometer in a Maserati 3200 is not uncommon. The tachometer is driven directly by the engine ECU so a malfunction can only be in one of three areas:
- The engine ECU
- The wiring
- The tachometer
The easiest way to check where the problem lies is to put an oscilloscope onto the tachometer signal (the green/black cable on the multi-plug directly behind the display):
You are looking for a square wave with an amplitude of approximately 6 volts, the frequency of which is directly proportional to the speed of the engine.
If there is no signal at the back of the instrument panel then put the oscilloscope onto pin 4 of connector D on the engine ECU. If there is a signal here then it is a wiring issue. No signal here means an internal issue with the ECU.
If there is a signal at the instrument cluster then the next check is to inspect the track shown below:
If the track is damaged then make good. If it is intact then the problem is with the tachometer itself. Given the abundance of used parts I prefer to buy a good used item rather then try and repair the motor.
Once the instrument cluster is on the bench then getting to the tachometer is straightforward.
Pull off the odometer reset and brightness control knobs:
This will allow the glass to be unclipped:
Carefully lever off the needles for the odometer and tachometer:
Unscrew the two little black screws on the face of the odometer:
Remove the three nuts on the back of the assembly as shown:
The tachometer, multi-function display and fascia can then be removed in one piece. Note that there are two clips that need to be prised away (shown in red on picture of the housing).
The tachometer can be unbolted from the facia if needed however I prefer to buy a complete used cluster and make one good one.
Once it is all back together, start the engine and admire your handiwork.
Please note that if you turn the ignition on with the instrument cluster removed then the airbag ECU will report errors for the absence of the warning lights which will need to be removed with an SD2.
Other posts in this category: Engine and Drivetrain
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Aldous Voice 